preoxygenation

[prē′ŏk-sĭ-jə-nāshən]
n.
  1. Administration of pure oxygen prior to induction of general anesthesia in order to eliminate nitrogen from the lungs and body tissues.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.